The present invention relates to an image developing unit used for electrophotography and an image forming apparatus provided with the image developing unit.
An image forming apparatus that adopts electrophotography has a photosensitive device, charging device, exposing device, image developing device, transferring device, and fixing device set in its apparatus body, in order to record an image on a recording sheet. The charging device charges the photosensitive device. The exposing device forms a latent image by exposing the photosensitive device. The image developing device forms a toner image by applying a toner to the photosensitive device to develop the latent image. The transferring device transfers the toner image on the photosensitive device to the recording sheet. The fixing device fixes the toner image on the recording sheet.
In this image forming apparatus, an image developing unit comprises the image developing device and a toner cartridge. The image developing device has a toner tank that stores a toner and a photosensitive device for supplying and applying the toner in the toner tank to the photosensitive device. The toner cartridge is stored with the toner. The toner is delivered from the toner cartridge and fed into the toner tank of the image developing device. To attain this, the toner tank of the image developing device is provided with supply means for feeding the toner delivered from the toner cartridge into the toner tank.
The toner tank includes a toner inlet that receives the toner supplied from the toner cartridge. The supply means includes a toner supply route that extends away from the toner inlet and receives the toner having passed through the toner inlet and conveyor means for transporting away from the toner inlet the toner received by the toner supply route. The toner supply route has a single toner supply port in the central portion with respect to its lengthwise direction (away from the toner inlet). This toner supply port makes the toner, transported through the toner supply route by means of the conveyor means, flow into the toner tank.
In the toner tank, an image developing roller is set extending parallel to the toner supply route, and an agitator is set between the toner supply route and the image developing roller so as to extend parallel to the toner supply route. The toner which flows out from the toner supply port of the toner supply route is transported to the image developing roller, and is agitated by rotation of the agitator.
In this conventional image developing unit, the toner is supplied from the toner supply port that is located in one position on the toner supply route to one place in the toner tank. The toner in the one place is dispersed covering the entire image developing roller in its axial direction and supplied to the image developing roller by rotation of the agitator. Thus, the dispersion of the toner, covering the entire image developing roller in its axial direction, depends on the agitator alone.
However, the dispersion of the toner in the one position by means of the agitator alone, covering the entire image developing roller in its axial direction, is limited, and the toner is transported to the image developing roller before it is fully agitated by means of the agitator and uniformly dispersed covering the entire image developing roller in its axial direction. Thus, the toner is supplied to the image developing roller in a manner such that it is concentrated on the one place in the axial direction of the image developing roller that corresponds to the toner supply port of the toner supply route. In other words, the toner is locally supplied to one portion of the image developing roller. In consequence, the image developing roller forms the toner image to supply the toner to the photosensitive drum locally, so that the image quality is lowered.
The object of this invention is to provide an image developing unit which is capable of easily and securely dispersing a toner delivered from a toner cartridge to cover an entire area of an image developing roller of an image developing device in its axial direction, thereby ensuring satisfactory image quality, and it is also an object of this invention to provide an image forming apparatus provided with such an image developing unit.
According to the invention an image developing unit is provided which comprises a toner cartridge and an image developing device wherein, the toner cartridge stores a toner and has a toner outlet through which the toner flows out, and the image developing device includes a toner tank having a toner inlet capable of receiving the toner flowed out from the toner outlet of the toner cartridge and a toner supply route extending away from the toner inlet and capable of receiving the toner flowed into through the toner inlet. A conveyor means is provided for transporting away from the toner inlet the toner received by the toner supply route, and an image developing roller is set in the toner tank. The toner supply route has a plurality of toner supply ports arranged away from the toner inlet so that the toner in the toner supply route flows out through the toner supply ports into the toner tank, and the respective aperture areas of the plurality of toner supply ports gradually increase with distance from the toner inlet.
According to the invention an image forming apparatus is provided which comprises an apparatus body, a photosensitive device, and an image developing unit including a toner cartridge and an image developing device. The toner cartridge stores a toner and has a toner outlet through which the toner flows out, and the image developing device includes a toner tank having a toner inlet capable of receiving the toner flowed out from the toner outlet of the toner cartridge and a toner supply route extending away from the toner inlet and capable of receiving the toner flowed into through the toner inlet. A conveyor means is provided for transporting away from the toner inlet the toner received by the toner supply route, and an image developing roller is set in the toner tank. The toner supply route has a plurality of toner supply ports arranged away from the toner inlet so that the toner in the toner supply route flows out through the toner supply ports into the toner tank, and the respective aperture areas of the plurality of toner supply ports gradually increase with distance from the toner inlet.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.